<!DOCTYPE html>
<html>
    <head>
        <meta http-equiv="X-UA-Compatible" content="IE=edge">
        <style>
            #counter-message.preload {
                display: none;
            }
            #counter-message {
                display: block;
            }
        </style>
    </head>
    <body>
        <h1 id="counter-message" class="preload"></h1>
        <script>
            var t;
            function init() {
                var h1 = document.getElementById('counter-message');
                h1.setAttribute('class', '');
                setCurrentCount(0);
                t = setTimeout(tick, 500);
            }

            function tick() {
                window.external.invoke('update');
                t = setTimeout(tick, 500);
            }

            function setCurrentCount(count) {
                if (count > 10) {
                    return window.external.invoke('exit');
                }
                var h1 = document.getElementById('counter-message');
                var rem = 11 - count;
                var suffix = rem < 2 ? ' second' : ' seconds';
                h1.innerText = 'Exiting in ' + rem + suffix;
                document.body.appendChild(h1);
            }
            external.invoke('init');
        </script>
    </body>
</html>